The decoys also were able to fully neutralize infection by SARS-CoV-2 (SARS-CoV-2 nanoLuc; see the materials and methods) in the lung epithelial cell line Calu-3 expressing both ACE2 and the transmembrane protease serine 2 (TMPRSS2) (35, 36) [median effective concentration < 5 nM at a multiplicity of infection (MOI) of 1.0; Fig. 5A]. Here, ACE2 is linked to infection.